1. Field of the Invention
The present invention relates to a linear guide rail and a method for working the same and, in particular, to an improvement in working of one or more raceway grooves of such linear guide rail.
2. Description of the Related Art
Conventionally, a manufacture of a linear guide rail is carried out through, for example, a step shown in FIGS. 15A to 15F. That is, steel material (work) used as a linear guide rail blank work is drawn to thereby form the outer shape of the linear guide rail as well as the shape of each of raceway grooves 2 (see FIG. 15A).
Next, the groove bottom portion of the raceway groove 2 of the thus drawn-worked linear guide rail work is cut to thereby form a wire holder groove 3 (or, in some cases, an oil storage groove) for insertion of a wire holder and/or a base surface display line (or a base surface display groove) 4 for displaying a mounting base surface Wbs (see FIG. 15B).
The above operations are executed as pre-working operations.
After then, the linear guide rail work is heat treated.
Next, the linear guide rail is bored to thereby make a mounting bolt hole 5 (see FIG. 15C).
Then, the upper surface Wa and lower surface Wc of the guide rail work are finish ground (see FIG. 15D).
Further, the raceway grooves 2 as well as the two side surfaces Wbs and Wb of the guide rail work are finish ground (see FIG. 15E). The groove grinding operation, as shown in FIG. 15F, is carried out by the simultaneous grinding operation of the two side surfaces of the guide rail work.
However, the above-mentioned pre-working operations, that is, the drawing and cutting operations provides working accuracy and surface roughness which are not sufficient as finish accuracy and, therefore, as a finishing step, there is necessary a grinding operation even in the case of a product which does not require high accuracy, which raises a problem that it takes long time to work the guide rail and thus the working cost of the guide rail becomes expensive.
That is, in the above drawing operation, there can be provided only the insufficient working accuracy and thus, in the grinding operation, it is necessary to provide rather large grinding allowance, which results in the longer grinding time. On the other hand, in order to work a guide rail as accurately as possible in the drawing operation, the number of times of drawing must be increased. In fact, however, each time the guide rail work is drawn, it is necessary to execute the following pre- and post-treatments: that is, (1) leader formation (a treatment to narrow the leading portion of the guide rail work so as to be insertable into a die); (2) annealing; (3) shot peening for removing scales developed in a heat treatment; and, (4) a phosphate film treatment. This raises a problem that the working cost of the guide rail is expensive and the working accuracy thereof is not so good.